These figures are our own. We calculated them from the Finnish Meteorological Institute’s open data: the daily observations of its weather station at Rovaniemi airport over the 28 years from 1998 to 2025, which is as far back as the open data for that station goes.1 The institute publishes the data under the CC BY 4.0 licence. The result is not the institute’s official long-term average, and how it was calculated is at the end of the page.
Month by month
The average day is the mean of the daily mean temperatures; the average night low and day high are the means of the daily minimum and maximum. The last two columns count how many nights fell to minus twenty or below, and give the lowest reading in the 28 years.
| Month | Average day | Average night low | Average day high | Nights at −20 °C or colder | Lowest, 1998–2025 |
|---|---|---|---|---|---|
| January | −10.6 °C | −13.8 °C | −7.7 °C | 22 % | −38.1 °C |
| February | −9.9 °C | −12.9 °C | −7.0 °C | 18 % | −33.9 °C |
| March | −5.5 °C | −9.0 °C | −1.8 °C | 4 % | −23.3 °C |
| April | 0.5 °C | −3.2 °C | 4.5 °C | 0 % | −19.2 °C |
| May | 7.0 °C | 2.8 °C | 11.6 °C | 0 % | −8.0 °C |
| June | 12.9 °C | 8.8 °C | 17.4 °C | 0 % | −1.0 °C |
| July | 16.1 °C | 12.1 °C | 20.6 °C | 0 % | 3.0 °C |
| August | 13.3 °C | 9.8 °C | 17.5 °C | 0 % | 0.4 °C |
| September | 8.3 °C | 5.4 °C | 11.7 °C | 0 % | −4.7 °C |
| October | 1.3 °C | −0.7 °C | 3.7 °C | 0 % | −16.3 °C |
| November | −4.3 °C | −6.7 °C | −2.0 °C | 3 % | −24.8 °C |
| December | −7.7 °C | −10.6 °C | −5.1 °C | 11 % | −30.7 °C |
What the averages hide
An average of minus ten in January sounds manageable, and on many January days it is. The column that matters more is the night column: more than one night in five in January reached minus twenty or below, and in February almost one in five. Counted as weeks, 53 % of all seven-day stretches in January included at least one such night, 46 % in February and 33 % in December.
Minus thirty is a different matter. In 28 years it came on 13 January nights, 9 February nights and a single December night, and those 23 nights fell in only eight of the winters. It is the reading people remember, not the one to plan a week around. The lowest of all was −38.1 °C, on 28 January 1999.
December is milder than January and February, with an average day of −7.7 °C, though a night at minus twenty still came on about one December night in nine. March is still full winter by the thermometer, with an average day of −5.5 °C, but a night at minus twenty is already rare.
